Nitride semiconductors used in semiconductor light emitting devices such as a light emitting diode (LED) are crystal-grown on a sapphire substrate by using a metal organic chemical vapor deposition method (hereinafter, referred to as “MOCVD method”), for example. In order to improve the light emitting characteristics of the semiconductor light emitting devices, it is important to improve the crystallinity of the nitride semiconductors.
On the other hand, a technique has been proposed in which a substrate having asperities is used to improve the light extraction efficiency in a semiconductor light emitting device (for example, refer to JP-A 2007-254175 (Kokai)).
However, it is difficult to evenly grow a crystal of a nitride semiconductor on the substrate having asperities because defects such as pits are likely to occur in the crystal on such a substrate. A special technique is required to evenly grow the crystal of the nitride semiconductor on the substrate having the asperities.